Polymeric compositions which are able to absorb and release volatile ingredients are well known in the art, in particular concerning perfume delivery.
GB1558960 from Nagae, describes a perfume emitting PVC film to be used in umbrellas.
U.S. Pat. No. 4,618,629 from T. Burnett & Co, Inc describes fragrance-emitting polyurethane foams which have a particulate fragrance-carrying resin incorporated in them. The resin can be selected from a list of polymers (polyolefins, polyester, PVC and similar, polyamides, cellulose polymers).
A common use of polymeric compositions for perfume delivery comprises for example air freshening devices. These are typically in the form of aqueous gels usually obtained from crosslinked polysaccharide polymers (starches, alginates or CMC) such as those described in GB2286531 from Kelco, U.S. Pat. No. 3,969,280 from Johnson & Johnson.
While these and other documents claim to provide long lasting delivery of volatile materials, they are still far from being fully satisfactory for a number of reasons.
Firstly, these polymeric compositions can normally incorporate and release a very limited amount of volatile material, in most cases not exceeding 10% of the total weight of the compositions.
Secondly these polymeric compositions are not able to release uniformly different components of the volatile material which have different volatilities. Given, for example, a perfume which can have more than 10 different components, the more volatile components will be released first and after some time only the less volatile notes would be perceptible, therefore the full perfume character would never be perceived by the user. Actually, the above mentioned polymeric compositions are commonly used to deliver simple perfumes, typically consisting of a single volatile substance such as citronellol as they are simply not capable to consistently deliver a more sophisticated perfume as is increasingly desired by the modern perfume industry.
Thirdly pure polymeric materials are difficult to transform and generally require high temperatures to be molded. Therefore whenever a volatile material is introduced in the melt, a large amount of said material is lost due to the high temperature.
The first and second problems have been partially addressed by Firmenich in U.S. Pat. No. 4,734,278 which describes shaped bodies of block polyether-amide based resins (e.g. Pebax™) that provide sustained release of volatile actives (perfumes, deodorants, insecticides etc). An improvement has been obtained by Atochem that in WO 9726020A1 describes improved fragrant resins made of Pebax™ plus a complex perfume (i.e. more than 5 components). Such resins are able to deliver a complex perfume with a reduced separation of the volatile ingredients over time.
The third problem has been only partially solved by the use of plasticizers which, as it is well known to those skilled in the art, allow the reduction of the processing temperature of polymeric mixtures. This solution has been applied e.g. by Avon in U.S. Pat. No. 4,552,693 which describes transparent fragrance-emitting articles obtained from compositions comprising a thermoplastic polyamide resin, a plasticizer/solvent system comprising a sulfonamide plasticizer, and a fragrance. The advantage of using a plasticizer in these compositions is the possibility of processing said compositions (molding, extruding, filming) at relatively low temperatures, as it is known for so called hot melt compositions.
Further improved compositions have been described in European Patent Appl. EP 1,153,169 assigned to Procter & Gamble Company which describes a polymeric material which is able to incorporate and sustainedly release volatile materials which are composed by several ingredients of different volatility for a long time and without separation of said ingredients during the release, and is also capable of being easily processed and formed into an article, preferably with hot melt techniques.
Another problem which is relevant when polymeric compositions capable of delivering a volatile material are to be incorporated into a product is their adhesion on substrates when applied e.g. in the molten state. In many cases, in fact, said polymeric compositions need to be applied on a substrate (e.g. the internal surface of a package, or a support surface on an air freshener device) on a high speed process line. In this situation it is clearly desirable not only that the polymeric compositions can be applied as a hot melt but also that said polymeric compositions have sufficient adhesion to remain in the desired point of application without the need for an additional source of adhesion such as an adhesive strip, or an additional hot melt glue to be applied onto the substrate before said polymeric composition in order to fix it on that. Prior art materials have to compromise between capability in delivering different volatile materials and effective adhesion properties in the molten state.
Prior art polymeric compositions are often based on specific pure polymers like polyether-polyamide block copolymers, pure polyamide polymers or pure EVA polymers. As a consequence the choice of the volatile material was limited to those ingredients which were soluble or compatible with that specific polymer.
In U.S. Pat. No. 5,861,128 a composition comprising an EVA polymer and a plasticizer is described. However the plasticizers suggested for use with EVA are only hydrocarbons (e.g. polybutene) and therefore the resulting compositions are able to incorporate only a limited number of perfume materials due to their low polarity.
U.S. Pat. No. 4,515,909 describes resinous compositions for the release of fragrant substances which are based on EVA and also contain up to 10% of the weight of the polymer of a perfume diffusing agent which can also be regarded as a plasticizer, but the low level at which it is used does not provide the composition with adhesion properties, in fact compositions described here are used in molds and are not adhesive.
Polymeric compositions which are able to incorporate and sustainedly release different volatile materials and which are also capable of being easily processed, typically as a hot melt, and which have a good adhesion on most polymeric and cellulosic substrates are described in our co-pending European Patent Appl. 04013513.
The present invention describes alternative compositions providing the same advantages as those described in European Patent Appl. 04013513, and having in addition improved adhesive properties.
The compositions of the present invention have in fact very good handling of high amounts of different volatile materials (high wt % storage, long sustained delivery times) combined with further improved adhesive properties which allow even easier application where needed for incorporation in a product in an industrial manufacturing process.